To go with what Ray suggests: I had the idea of taping negatives to your body for a day out in the sun. Come home at night and you're left with a lovely "tanned" image on your skin. Red results can be obtained by exposing too long... but there is the possiblity of skin cancer if you let the hobby get out of hand.

Alternativey, find yourself a sunscreen that can be imbibed to a gelatin matrix and "dye-transfer" that to your skin.